The preprocessor expression backend does not adhere to the VBA specification

[MDoerner]

Currently the backend for expression evaluation in the preprossessor does not follow the rules layed out in the VBA specification (section 2.1 and 5.6.9). This has the potential effect that we do not determine correctly which code is dead and which is not.

Most of the computations have an incorrect return type and the computations are not performed with the specified precision. (The backend seems to always use decimal.)

Moreover, the handling of octal and hex literals does not take into considerations that the value depends on the type suffix provided, e.g. &o100000 = -32768, but &o100000& = 32768.